1. Field of the Invention
The present invention relates to an optical pickup device, and particularly to an optical pickup device characterized by an optical pickup movement mechanism, and an optical disk device using the same.
2. Description of the Related Art
A movement mechanism for an optical pickup in a conventional optical disk device adopts a structure in which two guide shafts are provided in parallel to move the pickup, and the optical pickup is moved supported by the guide shafts.
For example, FIG. 5 shows a structure of a conventional optical pickup device. In the conventional optical pickup device 50, a main shaft 52 and a subsidiary shaft 53 which are metal drive shafts are provided as guide shafts respectively on two sides of a traverse mechanism chassis 51. Bearings 54a and 54b of a pickup base 54 on which an optical pickup 56 is mounted slide on the main shaft 52 and subsidiary shaft 53 as the guide shafts, kept in tight contact with these shafts by the deadweight of the optical pickup 56 or by a pressing spring force. In this case, a lubricant metal is incorporated in the bearing 54a on the side of the main shaft 52. On the other side, the bearing 54b on the side of the subsidiary shaft 53 has a structure in which the bearing 54b is directly formed in the pickup base 54. The pickup base 54 is molded mostly as a metal cast product.
An alternative known structure of the conventional optical pickup device is constituted by one metal guide shaft and a guide integrated with a resin-made traverse mechanism chassis provided in parallel with the guide shaft (e.g., an optical disk device SD-C2002 manufactured by TOSHIBA Corporation).
As described above, a metal shaft is used as the main shaft as a drive shaft among guide shafts. However, as the subsidiary shaft, a metal shaft is used in some cases or a guide integrated with a mechanism chassis is used in other cases.
As a countermeasure to prevent abrasion caused by slidable contact between a metal subsidiary shaft and a metal bearing, a resin material interposed between the subsidiary shaft and the bearing has been proposed (for example, see Jpn. Pat. Appln. Laid-Open Publications No. 2001-256739 and No. 2004-348794.
Conventional optical pickup devices have a mechanism in which an optical pickup is attached to metal guide shafts by a bearing provided in the optical pickup, to allow the optical pickup to slide on a guide shaft. Since the height accuracy and strength are necessary for the bearing, the bearing portion of the pickup is made of metal in many cases.
In addition, the bearing portion of the optical pickup on the side of the subsidiary shaft and a guide shaft are continuously in tight contact with each other. Hence, use of a metal guide shaft having high processing accuracy is necessary to prevent abrasion. As an alternative, use of a material having excellent slidability is needed in case of a guide portion integrated with a resin-made mechanism chassis. The former case of using a metal guide shaft involves problems such as an increased weight, necessity to polish surfaces of the shaft, and the like. The latter case of a guide portion integrated with a resin-made mechanism chassis involves a problem that strength of the mechanism chassis lowers.